SLAT161 June 2022 HD3SS3411 , TMUXHS4412
The PCIe standard specifies a 100 MHz clock (Refclk) with at least ±300 ppm frequency stability for Gen 1, 2, 3 and 4, and at least ±100 ppm frequency stability for Gen 5, at both the transmitting and receiving devices. It also specifies support for three different clocking architectures: Common Clock, Data Clock, Separate Reference Clocks.